package datastruct.tree;

import java.util.ArrayList;

/**
 * @author RunningShrimp
 * @date 2021/5/28  18:13
 * @see <a href=""></a>
 */
public class AvlTree<K extends Comparable<K>, V> {
    private Node root;
    private int size;

    public AvlTree() {
        root = null;
        size = 0;
    }


    public void add(K key, V value) {
        add(root, key, value);
    }

    private Node add(Node node, K key, V value) {
        if (node == null) {
            size++;
            return new Node(key, value);
        }
        if (node.key.compareTo(key) < 0) {
            node.left = add(node.left, key, value);
        } else if (node.key.compareTo(key) > 0) {
            node.right = add(node.right, key, value);
        } else {
            node.value = value;
        }

        return maintainBalance(node);
    }

    /**
     * // 对节点y进行向右旋转操作，返回旋转后新的根节点x
     * //        y                              x
     * //       / \                           /   \
     * //      x   T4     向右旋转 (y)        z     y
     * //     / \       - - - - - - - ->    / \   / \
     * //    z   T3                       T1  T2 T3 T4
     * //   / \
     * // T1   T2
     *
     * @param y
     * @return
     */
    private Node rightRotate(Node y) {
        Node x = y.left;
        Node T3 = x.right;

        //向右旋转的过程
        x.right = y;
        y.left = T3;

        //更新height值
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;

        return x;
    }

    /**
     * // 对节点y进行向左旋转操作，返回旋转后新的根节点x
     * //    y                             x
     * //  /  \                          /   \
     * // T1   x      向左旋转 (y)       y     z
     * //     / \   - - - - - - - ->   / \   / \
     * //   T2  z                     T1 T2 T3 T4
     * //      / \
     * //     T3 T4
     *
     * @param y
     * @return
     */

    private Node leftRotate(Node y) {
        Node x = y.left;
        Node T2 = x.left;

        //左旋转过程
        x.left = y;
        y.right = T2;

        //更新height值
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;

        return x;

    }

    private Node minimum(Node node) {
        if (node == null) {
            return null;
        }
        return minimum(node.left);
    }

    private Node removeMinim(Node node) {
        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }
        node.left = removeMinim(node.left);
        return node;
    }


    public V remove(K key) {
        Node node = getNode(root, key);
        if (node != null) {
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    private Node remove(Node node, K key) {
        if (node == null) {
            return null;
        }
        Node retNode;
        if (key.compareTo(node.key) < 0) {
            node.left = remove(node.left, key);
            retNode = node;
        } else if (key.compareTo(node.key) > 0) {
            node.right = remove(node.right, key);
            retNode = node;
        } else {
            // 待删除节点左子树为空的情况
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                retNode = rightNode;
            }

            // 待删除节点右子树为空的情况
            else if (node.right == null) {
                Node leftNode = node.left;
                node.left = null;
                size--;
                retNode = leftNode;
            } else {

                // 待删除节点左右子树均不为空的情况
                // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
                // 用这个节点顶替待删除节点的位置
                Node successor = minimum(node.right);
                successor.right = remove(node.right, successor.key);
                successor.left = node.left;

                node.left = node.right = null;

                retNode = successor;
            }
        }

        if (retNode == null) {
            return null;
        }
        return maintainBalance(retNode);
    }

    /**
     * 维护树的平衡
     *
     * @param node
     */
    private Node maintainBalance(Node node) {
        node.height = 1 + Math.max(getHeight(node.left), getHeight(node.right));
        int balanceFactor = getBalanceFactor(node);

        if (Math.abs(balanceFactor) > 1) {
            System.out.println("unbalanced:" + balanceFactor);
        }

        //维护平衡
        //LL
        if (balanceFactor > 1 && getBalanceFactor(node.left) >= 0) {
            return rightRotate(node);
        }
        //RR
        if (balanceFactor < -1 && getBalanceFactor(node.right) <= 0) {
            return leftRotate(node);
        }
        //LR
        if (balanceFactor > 1 && getBalanceFactor(node.left) < 0) {
            node.left = leftRotate(node.left);
            return rightRotate(node);
        }
        //RL
        if (balanceFactor < -1 && getBalanceFactor(node.right) > 0) {
            node.right = rightRotate(node.right);
            return leftRotate(node);
        }
        return node;
    }

    public boolean contains(K key) {
        return getNode(root, key) != null;
    }


    public V get(K key) {
        Node node = getNode(root, key);
        if (node == null) {
            return null;
        }
        return node.value;
    }


    public void set(K key, V value) {
        Node node = getNode(root, key);
        if (node != null) {
            node.value = value;
        }
    }


    public int getSize() {
        return this.size;
    }


    public boolean isEmpty() {
        return this.size == 0;
    }

    public boolean isBinarySearchTree() {
        ArrayList<K> keys = new ArrayList<>();
        inOrder(root, keys);

        for (int i = 0; i < keys.size(); i++) {
            if (keys.get(i - 1).compareTo(keys.get(i)) > 0) {
                return false;
            }
        }
        return true;
    }

    public boolean isBalance() {
        return isBalance(root);
    }

    private boolean isBalance(Node node) {
        if (node == null) {
            return true;
        }
        int balanceFactor = getBalanceFactor(node);
        if (Math.abs(balanceFactor) > 1) {
            return false;
        }
        return isBalance(node.left) && isBalance(node.right);
    }

    private void inOrder(Node node, ArrayList<K> keys) {
        if (node == null) {
            return;
        }
        inOrder(node.left, keys);
        keys.add(node.key);
        inOrder(node.right, keys);
    }

    private int getHeight(Node node) {
        if (node == null) {
            return 0;
        }
        return node.height;
    }

    private int getBalanceFactor(Node node) {
        if (node == null) {
            return 0;
        }
        return getHeight(node.left) - getHeight(node.right);
    }

    private Node getNode(Node node, K key) {

        if (node == null) {
            return null;
        }

        if (key.equals(node.key)) {
            return node;
        } else if (key.compareTo(node.key) < 0) {
            return getNode(node.left, key);
        } else {
            return getNode(node.right, key);
        }
    }

    private class Node {
        public K key;
        public V value;
        public Node left;
        public Node right;
        private int height;

        public Node(K key, V value) {
            this.key = key;
            this.value = value;
            left = null;
            right = null;
            height = 1;
        }

        @Override
        public String toString() {
            return key.toString() + " : " + value.toString();
        }
    }
}
